I use Google Chrome for pretty much everything. I love using the address bar=search bar in conjunction with Ctrl+L/Ctrl+T to make searches faster. I love how I don't have to wait 10-20 seconds for Chrome to open after I click the icon, unlike my experiences with Firefox. Chrome also utilizes screen space so much better than Firefox.
Firefox has a lot of extensions that are pretty useful though. Chrome only got extensions this January, so it can't really match Firefox in that category yet, but given time I'm sure they'll build up a good enough library of useful extensions. Chrome also seems to load pages faster than Firefox for me. Both have excellent keyboard shortcuts. IE 8 seems to be much improved compared to older versions, but I'd rather use Chrome or Firefox. IE's Ctrl+L is terrible.
Also, I found some preview screenshots of Firefox 4. They seem to have adopted a look similar to Chrome, and it looks pretty promising!
Their speeds should also improve significantly as compared to their current builds. Man, if it actually opens as fast as Chrome does, I'll switch back.
And despite how terrible IE has usually been for me, I'm actually interested in IE9. It'll be making use of your graphics card while rendering pages, which should provide a richer browsing experience, and its reported to load pages a LOT faster than IE 8.